Hello - I wanted to follow up on this posting to thank the 15 or so folks who responded. Most of what I heard was along the lines of "we are observing similar topshim behavior on our system(s). Please let me know what you find out on this topic."
The bad news is I did not get a solution to the problem and so this behavior lives on. The good news is that it sounds like the Bruker developers are aware of and are working on this issue. Thus, I am optimistic an update and improved behavior will be part of the next TopSpin release.
Thanks again everyone!
Mike
From: AMMRL List <ammrlrev_at_webserver2.chem.hawaii.edu>
Sent: February 15, 2023 3:28 PM
To: ammrlrev_at_webserver2.chem.hawaii.edu
Subject: AMMRL: TopShim 2.2.0
CAUTION: The Sender of this email is not from within Dalhousie.
Dear Colleagues:
We have recently had the good fortune of installing two new Neo systems; a 400 and a 500 both with SampleCase's. As a result, I have said good-bye to TS2.1.8 and am getting familiar with TS4.1.4. With this jump in TopSpin comes a large jump and revamping of TopShim (1.2.2 --> 2.2.0). Because TopShim looks quite different to me now in its reporting , Ive been watching it perform and report on both of these walk-up systems with some regularity.
I have noticed on both of these new systems with RT probes (400 with a BBFO iProbe and 500 with BBFO SmartProbe) that TopShim's behavior is usually as follows:
* Iteration 1 is robust and results in a large improvement in homogeneity, usually ending up with a FWHM somewhere around 0.4-0.5 Hz
* About 75-80% of the time, what follows is ~ 5 iterations where the FWHM oscillates between ~ 0.3 and 0.9 Hz, resulting in the message "slow convergence detected, shimming aborted. Using the best result as the final shim state". When I look at the maps, it appears that in the final 5-6 iterations TopShim is trying to deal with the effects out at the edges and is unable to do so reliably.
* I have noticed on both of these systems that z8 does not reliably converge but instead oscillates +/- 2000 units, on consecutive TopShim runs on the same sample. This is despite both of these systems having a BOSSIII shim system where ordmax=8 is supposed to be used according to documentation.
* This behavior is independent of the TopShim observe nucleus (1H/2H).
I am considering using the "fastfine" option on walk-up samples but what I'd really love to know is how I might tweak TopShim such that the above behavior is the exception rather than the rule. Is this a matter of using the zrange option to avoid the edges and thus shrink the region over which flattening is performed but where the hump is still tolerable?
Id love to hear the group's thoughts on this topic. I should be clear that the results we are obtaining from these two systems are absolutely fantastic! This email is just about me (possibly down a rabbit hole) wondering if with a deeper understanding even more can be gained.
Thanks!
Mike
Michael D. Lumsden
Nuclear Magnetic Resonance Research Resource
Department of Chemistry, Dalhousie University
6274 Coburg Road
P.O. Box 15000
Halifax, Nova Scotia, Canada
B3H 4R2
Phone: 902-494-1635
FAX: 902-494-1310
Web: http://www.dal.ca/diff/nmr3.html
Received on Tue Feb 28 2023 - 11:58:12 MST